In a typical cellular wireless communication system, a radio access network (RAN) includes a plurality of base stations, each of which radiates to define one or more coverage areas (cell sectors) in which mobile stations served by the RAN can thereby obtain connectivity with broader networks such as the public switched telephone network (PSTN) and the Internet.
A RAN will typically communicate with served mobile stations according to an agreed air interface protocol, examples of which include CDMA (e.g., 1×RTT or 1×EV-DO), iDEN, WiMAX, LTE, GSM, HSDPA, and others now known or later developed. Communications in the direction from the RAN to mobile stations define a “forward link”, while those in the direction from mobile stations to the RAN define a “reverse link”.
Air interface communications in each sector may occur on one or more frequency channels. Further, on each frequency channel, the air interface in each sector may be divided into a number of channels for carrying bearer traffic (e.g., voice and other user data) and control data between the base station and served mobile stations. Depending on the wireless technology used, the air interface can be divided into these channels through code division multiplexing (with each channel defined by modulation with a specific code), time division multiplexing (with each channel defined as a segment of time), frequency division multiplexing (with each channel defined by modulation with a specific frequency), and/or some other mechanism.
In terms of control channels, for instance, on each frequency channel, the forward link of each sector may define a pilot channel on which the RAN broadcasts a pilot signal for use by mobile stations to detect and evaluate coverage of the sector, one or more broadcast channels on which the base station transmits system parameters for the sector, and one or more paging channels on which the base station may broadcast system information as well as page messages targeted to specific mobile stations. Further, the reverse link of each sector may define one or more access channels on which mobile stations can transmit requests to establish calls (e.g., voice calls or data communication sessions) and responses to control channel messages received from the base station.
As a mobile station moves about in such a system, the mobile station may evaluate pilot signals in order to identify a strongest sector in which the mobile station should operate. Once the mobile station has identified that sector, the mobile station may then operate in an “idle” mode (also known as “dormant” mode) in the sector. When idling in a sector, the mobile station is not actively engaged in a call, but the mobile station periodically monitors a paging channel in the sector to receive any relevant page messages.
To enable the RAN to know where to page an idle mobile station, the mobile station may transmit a registration message to the RAN each time the mobile station moves into a new sector. When a RAN seeks to connect a call or other communication to the mobile station, the RAN may then transmit a page message to the mobile station in the sector where the mobile station last registered.
Alternatively, groups of sectors in the RAN may be designated as discrete paging zones, and the RAN may broadcast in each sector a paging-zone ID indicating the sector's paging zone. When an idle mobile station moves from one sector to another, the mobile station may then determine based on the paging-zone ID whether the mobile station has moved into a new paging zone and if so may transmit a registration message to the RAN. When the RAN seeks to connect a call or other communication to the mobile station, the RAN may then transmit a page message to the mobile station in all of the coverage areas of the paging zone where the mobile station last registered.
As noted above, each sector in the RAN may operate on one or more frequency channels and, on each frequency channel, may define one or more paging channels. At issue when an idle mobile station enters a new sector may therefore be which paging channel the mobile station should monitor for page messages. Likewise, from the base station perspective, at issue may be which paging channel in a given sector the base station should use to page the mobile station.